Gas activated treatment of elastic filaments



Jan. 28, 1969 H. E. HARRIS E A 3,424,828

GAS ACTIVATED TREATMENT OF ELASTIC FILAMENTS Filed Sept. 13, 1966 ACONTROL SAMPLE, 25C

GASEOUS HCI,

O IN AN ATMOSPHERE OF $12 xwozEw 6 F525 FIG. I.

WEIGHT, GRAMS mwI02 Iokmmkm mwkuz IPwZmJ WEIGHT, GRAMS w Y m S ms N NRR. E O WAN T IH W 5 G W m NW A! E United States Patent 9 Claims ABSTRACTOF THE DISCLGSURE The denier of synthetic elastic segmented polyurethanefilaments is reduced by the process of stretching the filaments adesired amount, exposing the filaments while in a stretched condition toan atmosphere of an activating gas and then desorbing the gas from thefilaments.

The present invention relates to a method for altering the physicalcharacteristics of shaped structures of elastorneric polymers. Moreparticularly, the invention relates to a method for imparting apermanent shape to synthetic elastic filaments.

Since the advent of elastic filaments, such as those composed ofsegmented polyurethane elastomers, there has been a wide application ofthese filaments in the manufacture of textile products. Because of thepeculiar spinning characteristics involved in the preparation of thesefilaments, it has been found more advantageous economically to spinlarge denier filaments and later reduce the denier of such filaments.

Various processes have been employed in the past to reduce the denier ofhigh denier elastomeric filaments, generally referred to as spandexyarn. All of these processes involve stretching the spandex to apredetermined length and subjecting the yarn to a heat treatment to heatset the yarn in its stretched condition. These heat-treatment processes,unless controlled carefully, cause harmful effects which lower thequality of the yarn. Therefore, it would be advantageous to employ amethod for reducing the denier of spandex yarn without the applicationof heat.

It is therefore an object of the present invention to provide a methodfor permanently reducing the denier of synthetic elastic filamentswithout heat-setting said filaments.

Another object of the present invention is to affect a permanent changein the size and shape of synthetic elastic filaments such as spandexwithout subjecting said filaments to the harmful action of hightemperatures.

Another object of the present invention is to provide an improved methodfor altering the physical properties of synthetic elastic filaments.

Another object of the present invention is to provide a method forimparting permanent shapes to synthetic elastic shaped articles.

Other objects and advantages of the invention will become apparent fromthe description to follow.

The objects of this invention are accomplished by altering the physicalcharacteristics of synthetic elastic filaments composed of asubstantially linear segmented polyurethane elastomer which comprisesapplying tension on the filament in an amount sufiicient to reduce thedenier thereof to a desired size and treating the filament with agaseous activator which includes sorption and desorption of said gaseousactivator. The filaments may be made to retain other shapes orconfigurations as, for example, a crimped condition by exposure to agaseous activator and the subsequent removal of the sorbed gas.Absorption may be carried out under conditions ranging from about 100 to1000 mm. of Hg and 0 to 50 C.

3,424,828 Patented Jan. 28, 1969 depending upon the rate of absorptiondesired. It was found that increased pressure and temperature produce amore rapid rate of absorption of the gas up to an equilibrium point.Removal of the gas can be accomplished by such methods as exposing thetreated sample to vacuum, heat, or a water bath. Preferably theabsorption is conducted under substantially anhydrous conditions.

The gaseous activators which may be employed with the present inventionmust be strong enough as Lewis acids to complex with the basic unitscomprising the synthetic elastic filaments. Such activators include thehydrogen halides, boron trifluoride, sulfur dioxide, and chlorine.Hydrogen chloride is the preferred activating gas, however, because ofits faster absorption and desorption rate and comparative ease ofhandling in a continuous process.

The process of this invention is not limited to any specific type ofsegmented polyurethane elastomer. Such elastomers are generally preparedby a process which comprises reacting a polymeric diol with an organicdiisocyanate and thereafter extending with a compound containing twoactive hydrogen atoms. The diols may be a polyether glycol such aspolyalkylene ether glycols, polyalkylenearylene ether glycols,polyalkylene etherthioether glycols, and the like, or polyester glycolsincluding polyester glycols derived from caprolactone, either with orwithout internal extension. The diisocyanates employed are generallyarylene diisocyanates and it has been found preferred to employ a paraoriented symmetrical aromatic diisocyanate. The chain-extending agent isa compound having two active hydrogen atoms as determined by the testdescribed in I. Am. Chem. Soc. 49, 3181 (1927). Such compounds may bediols or diamines. Ordinarily, the diamines are preferred. The reactantsused in preparing such polyurethane elastomers, including the glycol,the organic diisocyanate, and the chain-extending agent, are all wellknown in the art. See for example, US. Patent 2,871,227 to Walter and3,115,- 384 to Cacella et al.

In accordance with the present invention, the process may be conductedin conjunction with a spinning process which is employed to producecontinuous spandex filaments. The spandex filaments usually are receivedfrom the drying rolls and advanced through a sorption chamber filledwith the gaseous activator. Preferably, the chamber should be maintainedat approximately room temperature to provide uniform treating conditionsand handling convenience although substantially higher or lowertemperatures may be employed with somewhat less favorable results. It isdesirable to maintain a pressure on the chamber of about 200 to 800 mm.of Hg but almost any pressure range may be employed where found to beconvenient or practical. Thereafter, the spandex filament containing thegas absorbed in the sorption chamber is washed in a neutral or slightlybasic water bath to remove the gas. Another effective method forremoving the gas is by heating to above about 50 C. Higher temperaturesmay be employed, but precautions should be taken against heatdegradation of the filament properties.

Yarns treated in accordance with the process of this invention exhibitpermanent changes in size or configuration and improved physicalproperties such as tenacity and modulus. It is thought that the gaseousactivatoF disrupts the hydrogen bonds between the urethane and/or ureagroups to form a complex therewith which permits molecular flow orshifting of these groups to relieve stress imposed by tension orpressure on the filamentary structure. The complex formation isreversible and therefore the filamentary structure will assumepermanently the '2 a shape possessed at the time the gaseous activatoris removed.

This invention can be further illustrated by the following exampleswhich are intended to be illustrative only.

EXAMPLE I In the preparation of sample yarn for illustrating certainaspects of the invention, 3990 grams of a polyester diol having amolecular weight of 2838 prepared from 3 moles of polycaprolactone ofmolecular weight 830 internally extended with 348 grams of tolylenediisocyanate, was dissolved in dimethylformamide with 735 gramsp,p-methylenedi(phenyl isocyanate) to form a prepolymer solution havinga solids content of about 65 percent. A second solution was prepared byadding 30.1 grams of ethylenediamine to 8370 grams of dimethylformamide.The first solution was added to the second solution with agitation whilemaintaining the temperature at 45 C. After 2510 grams of the firstsolution had been added, the addition was stopped and the solution had aBrookfield viscosity of 37,000 centipoises at 25 C. and containedapproximately 15.0 percent solids. The resulting dope was filtered andwet-spun by extrusion through a 15-hole, 5 .5-mil holesize spinneret.The coagulating bath contained 75 percent H and 25 percent solvent andwas maintained at a temperature of 80 C. The filament bundle was drawnfrom the bath, washed substantially solvent free in a hot water bath,and dried on heated rolls at 135 C.

A sample of the yarn was suspended on a Worden fused quartz spring in agaseous sorption apparatus. The sysl tern was evacuated to 0.5 mm. ofHg. After one hour the system was filled to atmospheric pressure withanhydrous hydrogen chloride (HCl) gas at 25 C. The increase in weight ofthe spandex sample was followed by the elongation of the spring.

Spandex yarn rapidly absorbed HCl under these condi- Q tions up to about12% by weight. The detailed results were as follows:

Time, sec. Wt., mg. Wt. gain, mg. Wt. gain,

percent was evacuated to 0.5 mm. of Hg at C. The spandex lost most ofits sorbed HCl as shown below.

Time, sec. Wt., mg. Wt. gain,* mg. Wt. gain,

percent paratus was heated to 54 C. The spandex lost essentially all ofits sorbed HCl as indicated in the table below.

Time, sec. Wt., mg. Wt. gain, mg. .Wt gain,

percent Wt. gain compared to original Weight.

The same sample of spandex yarn was resubjected to thesorption-desorption procedure. The results obtained were essentiallyidentical to those obtained with the first experiments.

4 EXAMPLE IV Time, sec. Wt. of sample, mg. Wt. gain, mg. Wt. gain,

percent The pressure of HCl gas was increased to 366 mm. of Hg. Withinthree minutes the yarn sorbed to equilibrium at this pressure. The dataare shown below.

Time, sec. Wt. of sample, mg. Wt. gain, mg. Wt. gain,

percent The pressure of HCl was increased to 744 mm. of Hg. The spandexyarn sorbed HCl to a weight gain of about 12%.

The sorption apparatus was subjected to evacuation until the pressure ofHCl was reduced to 286 mm. of Hg. After three minutes the spandexretained only 6.1 percent weight gain of HCl. This value agreesreasonably well with the value of 7 percent weight gain found byapproaching this HCl pressure from the low side. Thus, it can beconcluded that the amount of sorbed gas is dependent upon the pressureemployed in the chamber during exposure.

EXAMPLE V Several 5-inch lengths of spandex yarn were mounted stretchedto 20 inches on a glass rod. The rod was placed in a sorption vesselwhich was subsequently evacuated to 0.5 mm. of Hg. After one hour thesystem was filled to atmospheric pressure with anhydrous HCl gas. After15 minutes the system was again evacuated to 0.5 mm. of Hg for one hour.The yarn was washed in water to remove the last traces of HCl. Thesamples when removed from rod were 16 inches in length had a decreaseddenier and increased tenacity. Results of physical testing were asfollows:

Sample Denier Ultimate Ultimate tenacity, gJd. e1ong., percent 314 0. 93248 310 0. 88 240 3 318 0. 78 233 Untreated 902 0. 68 571 EXAMPLE VISeveral samples prepared as described in Example V were examined afterbeing placed unrestrained in boiling water for 15 minutes. The averagedenier of these samples was 345 before and 471 after the treatment.

EXAMPLE VII Several samples of spandex yarn were treated as follows. Aone-inch sample was mounted in the sorption apparatus to support acertain weight and the extension of the yarn as a function of thisweight was measured in air at 25 C. The vessel was then evacuated to 0.5mm. of Hg and after one hour the system was slowly filled to atmosphericpressure with anhydrous HCl gas. The

weight-supporting yarn began to elongate, rapidly reaching a maximumvalue depending on the supported weight. For example, a sample of yarnsupporting 100 grams stretched to 4.5 inches in air, but in anatmosphere of HCI stretched to inches. Additional results are shown bythe curves plotted in FIGURE 1. These data illustrate that the yarnstretches more readily when exposed to the gaseous activator.

After about seconds exposure the sorption vessel was again evacuated to0.5 mm. of Hg for one hour to desorb HCl. Upon removal from theapparatus the yarn was washed in Water to remove residual HCl. Thesesamples thus stretched in an atmosphere of HCl assumed a new increasedlength depending on the supported weight. For example, the samplesubject to HCl sorption-desorption while supporting 100 grams was 3.5times its original length after removal of the weight. The results forseveral samples are shown by the curves plotted in FIG- URE 2.

EXAMPLE VIII Several yards of spandex yarn were coiled onto two glassrods of /3 inch diameter. Each rod was put into a sorption vessel whichwas subsequently evacuated to 0.5 mm. of Hg. After one hour the firstvessel was filled with gaseous HCl to atmospheric pressure. After 15minutes this vessel was evacuated to 0.5 mm. for one hour and bothsamples were subsequently Washed in water. The second vessel was at notime exposed to HCl.

The spandex yarn that was exposed to HCl retained the coiled shape afterremoval from the rod. However, the sample from the second vessel showedno sign of coil retention.

EXAMPLE IX A sample of the HCl-treated spandex yarn of Example V wastested according to standard procedures. The following results wereobtained.

It will be apparent from the foregoing illustrative examples to thoseskilled in the art that the present invention may be employed to alterthe shape and physical properties of synthetic elastic filaments.Further it will be apparent that improved properties other than thoseenumerated can be obtained from the practice of the invention set forthor the modification and changes thereto which will be obvious from thedisclosure made herein.

We claim:

1. A process for permanently reducing the denier of synthetic elasticsegmented polyurethane filaments which comprises attenuating saidfilaments, exposing said filaments to an atmosphere of an activating gasand then desorbing said gas from said filaments.

2. The process of claim 1 in which the activating gas is a hydrogenhalide.

3. The process of claim 1 in which the activating gas is borontrifluoride.

4. The process of claim 1 in which the activating gas is sulfur dioxide.

5. The process of claim 1 in which the filaments are stretched from 2 to7 times original length prior to exposure to the activating gas wherebythe denier of said filaments is permanently reduced upon desorption ofsaid gas.

6. The process of claim 2 in which the activating gas is hydrogenchloride.

7. A process for permanently reducing the denier of a synthetic elasticfilament composed of a substantially linear segmented polyurethaneelastomer which comprises applying tension to said filaments sufficientto reduce the denier a predetermined amount, exposing the filament to anatmosphere of an activating gas while under said tension wherein gas isabsorbed by said filament, and thereafter desorbing said gas from thefilaments.

8. The process of claim 7 in which the activating gas is a hydro-genhalide.

9. The process of claim 8 in which the hydrogen halide is hydrogenchloride.

References Cited UNITED STATES PATENTS 2,876,524 3/ 1959 Reyerson et a1.264-83 3,154,611 10/1964 Dinbergs 264176 3,242,244 3/1966 Maly 264--83JULIUS FROME, Primary Examiner.

I. R. T-HURLOW, Assistant Examiner.

US. Cl. X.R.

